This invention relates to heat recovery ventilators used to obtain thermally efficient ventilation of buildings and dwellings, and in particular, to those ventilators including rotary wheel heat exchangers.
Heat exchangers are used in ventilation systems installed in residential, commercial and industrial buildings to extract and remove heat and/or moisture from one air stream and transfer the heat and/or moisture to a second air stream. In particular, rotary wheel heat exchangers are known wherein a wheel rotates in a housing through countervailing streams of exhaust and fresh air, in the winter extracting heat and/or moisture from the exhaust stream and transferring it to the fresh air stream. In the summer, rotary wheel heat exchangers extract heat and moisture from the fresh air stream and transfer it to the exhaust stream, preserving building air conditioning while providing desired ventilation.
Fans or blowers typically are used to create pressures necessary for the countervailing streams of exhaust and fresh air to pass through the rotary wheel heat exchanger. Some ventilators, however, are designed for use in existing heating, ventilating, and air conditioning (HVAC) systems which have sufficient air pressure to drive the countervailing streams, and may or may not also include fans or blowers.
Various media have been developed for use in heat recovery ventilators to enhance heat and moisture transfer. Typically, heat exchangers in the prior art employ a plurality of parallel passages running in the direction of flow, such as shown in Marron et. al., U.S. Pat. No. 4,093,435 and Coellner, U.S. Pat. No. 4,594,860. Such passages must be sufficiently small to maximize the total surface area for heat transfer, yet sufficiently large relative to their length to minimize resistance to gas flow. These constraints have made the materials used as the heat exchanger media critical to the effectiveness of such rotary wheel heat exchangers. A continuing need exists for improved heat exchanger media and improved designs for rotary wheel heat exchangers which will increase the efficiency of heat transfer between the countervailing air streams, and will avoid the exacting material and design restrictions found in the prior art.
The pursuit of thermally efficient ventilation for rooms and buildings using rotary wheel heat exchangers has produced many heat recovery ventilators which are rather large, non-portable, and require fixed installation, such as the heat exchanger disclosed by Pennington, U.S. Pat. No. 2,807,258. A number of somewhat smaller, non-portable heat recovery ventilators have been developed using rotary drum-type heat exchangers, such as that of Munters, British Patent No. 738211. An even more compact window-mountable ventilator employing, however, a stationary heat exchanger, has been developed by Becker, U.S. Pat. No. 4,874,042. Nonetheless, the need continues to exist for compact, portable heat exchangers and heat recovery ventilators which can achieve thermally efficient ventilation, and which may be used without requiring modification of existing buildings or ductwork in residential, commercial and industrial environments.
Thermally efficient ventilation of residential, commercial and industrial buildings is of increasing importance. In addition to ordinary ventilation requirements, ventilation is needed to remove the hazardous build-up of radon, formaldehydes, carbon dioxide and other pollutants which otherwise accumulate in enclosed areas from various sources. Such ventilation requirements present a further need for inexpensive, portable, compact, and yet efficient heat recovery ventilators, which are capable of window-mounting or connection to existing systems. Because homes, as well as businesses, are affected by such pollutants, the need also exists for such heat recovery ventilators to be consumer-oriented and easy to maintain.